Genomic Invasion and the Role of Behaviour in Rapid Evolution

我想抓住进化的过程，我的提议旨在测试当新的突变“入侵”时基因组会发生什么。这种入侵可以通过编码或调节基因活性的DNA片段的自发突变发生，也可以通过杂交从另一个种群或物种迁移基因发生。我特别感兴趣的是，生物体如何根据当时的条件调整其行为，以补偿这种基因组入侵的负面影响，并促进更快速的进化变化。具有选择优势的新突变的出现和传播是进化过程的核心，但在自然系统中观察这一过程非常具有挑战性，原因有两个：首先，检测到这种基因组入侵的可能性微乎其微，因为它们很少发生。第二，进化变化一直被认为是以非常缓慢的速度发生的，比研究人员的一生要长得多。我的提议利用了一个教科书上的快速进化的例子，这个例子就是现在正在发生在海洋田蟋蟀Teleogryllus oceanicus身上的。雄性蟋蟀通常用歌声来吸引雌性交配，但在夏威夷群岛，它们也会吸引一种致命的寄生蝇（Ormia ochracea）。最近，一种通过消除雄性翅膀上的发声结构而使雄性翅膀雌性化的突变出现并传播开来。它被称为扁翼，存在于两个种群中，似乎有不同的遗传起源。我的研究将会弄清楚，究竟是什么在这些不同人群的基因组中发生了变化，导致了这种突变的男性类型，它将测试基因组的其余部分是如何反应的。特别是，我将利用从野外收集的基因组DNA的时间序列来可视化和测试与突变紧密物理接近的基因是如何被“扫过”的，或者与基因组的其余部分同质化的。换句话说，当平翼突变侵入海洋T.基因组时，可能发生了两件事。第一种是附近的基因被拖了过来，现在在种群中被过度代表了，第二种是基因组其他部分的基因产生了与突变特别有效的表型效应，因此在突变的雄性中比在正常雄性中更有可能被发现。我从以前的工作中知道蟋蟀对它们的社会环境很敏感，特别是对雄性发出的声音是否存在很敏感。雌性和雄性都改变了它们的交配行为以适应当时的社会条件，我将测试一个假设，即扁翼突变能够更快地传播，以应对来自拟寄生物的选择，因为社会灵活性使蟋蟀能够应对变化的社会环境，也就是说，随着扁翼的出现，安静的环境变得越来越多。我在实验室里设计了一个蟋蟀追踪装置，它复制了野生环境，我可以用它来测试蟋蟀的行为和交配成功率。它包括视频和音频记录蟋蟀，并使我能够在试验中操纵相互作用的个体的组成。通过这种方式，我可以改变蟋蟀的社会经验，它们来自什么种群，以及不同变种的相对丰度，以测试社会灵活性如何有助于突变雄性的繁殖成功。这些试验的结果阐明了行为如何与进化过程相互作用，以及进化变化的速度如何受到社会环境和个体生物对环境的反应的影响。

LAY SUMMARYI want to catch evolution in the act, and my proposal aims to test what happens to genomes when novel mutations "invade". Such an invasion could occur through spontaneous mutation in a section of DNA that codes for or regulates the activity of a gene, or by migration of genes from another population or species due to hybridization. I am particularly interested in how the ability of an organism to adjust its behaviour depending on the prevailing conditions might compensate for negative effects of such a genomic invasion and facilitate more rapid evolutionary change.The emergence and spread of new mutations with a selective advantage is at the heart of the evolutionary process, but this process is extraordinarily challenging to observe in a natural system for two reasons: the first is that the likelihood of detecting such a genomic invasion is miniscule because they happen so rarely. The second is that evolutionary change has been thought to occur at a very slow pace, much longer than a researcher's lifetime. My proposal capitalises on a textbook example of rapid evolution that is occurring right now in the Oceanic field cricket, Teleogryllus oceanicus. Male crickets usually sing to attract females for mating, but in the Hawaiian archipelago, they also attract a deadly parasitoid fly (Ormia ochracea). Recently, a mutation that feminises male wings by erasing sound-producing structures on male wings arose and spread. It is called flatwing, and it exists in two populations and appears to have different genetic origins. My research will work out what, exactly, has changed in the genome of these different populations to cause this mutant male type, and it will test how the rest of the genome has responded. In particular, I will make use of a time-series of genomic DNA collections from the wild to visualise and test how the genes that lie in close physical proximity to the mutation get "swept" along with it, or become homogenized with the rest of the genome. In other words, when the flatwing mutation invaded the T. oceanicus genome, two things may have happened. The first is that genes nearby got dragged along and are now over-represented in the population, and the second is that genes in other parts of the genome produced phenotypic effects that worked particularly well with the mutation, and therefore are more likely to be found in the mutant variety of males than in normal males.I know from previous work that crickets are sensitive to their social environment, in particular, to the presence or absence of acoustic songs that males produce. Both females and males change their mating behaviour to suit the prevailing social conditions, and I will test the hypothesis that the flatwing mutation was able to spread in response to selection from parasitoids more rapidly because social flexibility enabled crickets to cope with the changed social environment, namely, the silent environment that emerged as flatwings became more numerous. I have devised a cricket tracking setup in the lab, which replicates the wild environment and which I can use to test cricket behaviour and mating success. It involves video and audio recording crickets, and enables me to manipulate the composition of interacting individuals during trials. In this manner, I can vary crickets' social experience, what population they are from, and the relative abundance of the different morphs, to test how social flexibility contributes to the reproductive success of mutant males. Results from these trials stand to illuminate how behaviour interacts with the evolutionary process, and how the rate of evolutionary change can be affected by the social environment and individual organisms' responses to that environment.